In order to control the temperature and air quality, in commercial and other buildings, building ventilation systems are utilized. These ventilation systems include a number of exhaust ventilators spaced throughout the building to withdraw air from the rooms in the building. Removal of the air from a room allows a separate heating and/or air conditioning system in the building to supply air to the room to effectively control the temperature.
The ventilators connected to the ventilation system are normally located directly above the ceiling of the room so that the ventilator can withdraw air from the room by means of a fan or blower mounted in the ventilator. After the air is drawn into the ventilator by the fan, the air is then discharged from the ventilator through an outlet opening in the ventilator housing. The outlet opening is connected to a ventilation duct by a duct connector at the outlet opening disposed in the ventilator housing. The ventilation duct leads from the ventilator to the exterior the building, allowing the air removed by the ventilator to be vented to the outside atmosphere.
As the duct connects the ventilator with the outside atmosphere, it is desirable to prevent air from the outside atmosphere from flowing through the ducts into the ventilator and back into the room from which the air was removed.
To this end, a damper flap is placed in duct or duct connector that opens to allow air flowing from the ventilator freely into the duct, but closes to block the passage of air flowing in the reverse direction from the outside atmosphere to the ventilator. A common damper flap construction comprises a flat plate that is hinged to the duct connector along one edge and covers the opening in the duct connector when in the closed position. To form the hinge, the damper flap is fastened along one edge to a rod that is mounted in spaced holes in the duct connector. Or, sleeves may be formed along an edge of the plate. Each sleeve receives one end of a pin inserted through the duct connector. The pins can be secured to the flap or duct connector to mount the flap in the connector.
However, damper flap and duct connector units of the above types are time consuming and expensive to fabricate and assemble, thereby increasing the cost of this component of the ventilator.